Thanks, Jon. Now wondering what's Putin's next move and how will the west respond? This high-stakes faceoff between Russian and American presidents has a familiar ring. For decades and decades, it was the stuff of nightmares. While we conduct missile drills. Both imagined -- The planes are fully armed with nuclear weapons. And real. Ordering an air and naval quarantine of Cuba. East versus west. Good versus evil. Spy versus spy. A United States air force plane shot down on Russian soil. A cold war with the hottest possible weapons at the ready. Massive nuclear arsenals to deter through fears ofy utuall assured destruction. That cold war came to a crashing end more than 20 years ago. But fast forward to today -- Cold war. Cold war. With more than 20,000 Russian troops on the border of Ukraine, and thousands more firmly in control of crimea, it is a sobering reminder that Russia remains a formidable foe. I don't want to be alarmist, but the situation is dangerous. It's combustible. President Putin has done something we have not seen in Europe since 1945, since the end of world war ii. The former vice chairman of the joint chiefs of staff, general James cartwright has the same concerns. This is worrisome. I can't equate this to anything over the last ten or 15 years. This is serious. It is an infraction and an incursion. But this is not the old cold war. The nuclear threat has faded. This is chapter two. The fallout from the shrinking soviet union, the expanse of nato, and the east's tilt toward Europe. This is about his vision for Russia. This is about his reconstructing the history of the cold war. It's a little bit of trying to reconstruct that, rebuild that, rebuild Russia's place in the world. Putin himself before the invasion giving George stephanopoulos what is now a haunting hint of what was to come. Translator: After the collapse of the soviet union, the society had a negative and pessimistic attitude. We have to pull ourselves together. That resolve to reassert the ways of old, says roger Cohen, is why the U.S. And the international community must keep up the pressure. We have not taken him seriously. The village that president Putin understands is a language of force. We are rediscovering that the nato alliance remains very important. And president Obama has made clear, if the most recent sanctions don't work, there will be more. Russia must know that further escalation will only isolate it further from the international community.

This transcript has been automatically generated and may not be 100% accurate.

{"id":23026153,"title":"'This Week': Cold War Redux ","duration":"3:00","description":"ABC News' Martha Raddatz examines the possibility of another Cold War with Russia.","url":"/ThisWeek/video/week-cold-war-redux-23026153","section":"ThisWeek","mediaType":"Default"}